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About the Year of Light

The International Year of Light is a global initiative which will highlight to the citizens of the world the importance of light and optical technologies in their lives, for their futures, and for the development of society. It is a unique opportunity to inspire, educate, and connect on a global scale.

Bullet Cluster 3.8 billion light years

This image of two colliding clusters of galaxies is a special snapshot that contains X-ray light, visible light, and the inferred presence of dark matter, the mysterious substance that pervades the Universe. The pink areas are where hot, X-ray emitting gas is found. The bending of light from distant background galaxies by the massive clusters shows astronomers the location of unseen dark matter. The combined image shows that hot gas has been ripped apart from the dark matter by the force of this colossal collision. Therefore, even though it does not emit light itself, dark matter gives clues about itself by the effect it has on light from cosmic sources.
Image Credit:
X-ray: M.Markevitch for NASA/CXC/CfA and visible light by D. Clowe for NASA/STScI; Magellan/U. Arizona and ESO
view and download image here.

Cassiopeia A 11,000 light years

One of the most famous bodies in the night sky is the Cassiopeia A supernova remnant. This object was created when a massive star ran out of fuel and exploded, hurtling its outer layers into space at millions of miles per hour. Because this material has been superheated, it glows brightly in X-ray light that is more energetic than what humans can see with their eyes. This image of Cassiopeia A was taken with NASA's Chandra X-ray Observatory and shows three different energy bands of X-ray light in red, green, and blue.
Image Credit:
NASA/CXC/SAO
view and download image here.

Comet Hale-Bopp 655 light seconds

When Comet Hale-Bopp passed through the inner part of our Solar System in 1997, it was bright enough that it could be seen without a telescope or binoculars for over a year. Many skywatchers may have wondered why there were two tails behind this comet. Comets are often referred to as "dirty snowballs" because they are balls of ice, dust, and rock. When one of these snowballs comes close to the Sun, it begins to heat up and lose dust and gas. The dust that evaporates from the comet follows the comet's orbit while reflecting the Sun's light, thus appearing white. The blue tail shines due to gas from the comet, primarily carbon monoxide, interacting with particles emitted by the Sun, and traces the path of those outflowing solar particles.
Image Credit:
Dan Schechter
view and download image here.

Cosmic Microwave Background 13.7 billion light years

The cosmic microwave background is the oldest light in the Universe, the afterglow of the Big Bang. This ancient light arrives to us not as the type of light we can see with our eyes, but in the form of microwaves, a type of light with wavelengths between radio and infrared light. This image was made by the WMAP satellite and shows the whole sky unfolded onto a flat image. The different colors show tiny variations in temperature that existed when the Universe was about 380,000 years old, and had cooled enough after the Big Bang for light to pass. These fluctuations are thought to be the structures that eventually formed into galaxies.
Image Credit:
NASA/WMAP Science Team
view and download image here.

Eagle Nebula 7,000 light years

Our Galaxy is filled with giant gas clouds containing atoms of hydrogen, carbon, oxygen, and other heavy elements–the building blocks out of which new stars and planets are made. These atoms can be energized–either from ultraviolet light from nearby stars or by collisions with other particles–and the extra energy may be released as light of very specific wavelengths. Astronomers look for the emission of particular elements in distant objects by using special filters on their telescopes. This image, made at the Kitt Peak National Observatory in Arizona, features the Eagle Nebula, or Messier 16, in all of its glory. This view shows a central cluster of stars that is forming within a larger hollow shell of gas and dust. The colors represent light given off by glowing hydrogen (green), oxygen (red), and sulfur (blue).
Image Credit:
T.A, Rector/University of Alaska Anchorage and B.A. Wolpa (NOAO/AURA/NSF) view and download image here.

This website was developed by Lightsources.org, a collaboration between communicators from light source facilities around the world.

IYL2015 is a global initiative adopted by the United Nations to raise awareness of how optical technologies promote sustainable development and provide solutions to worldwide challenges in energy, education, agriculture, communications and health.